A better integration of "Rate of Perceived Exertion" (RPE) within Regular workout design
A better integration of RPE would include a designated field for trainers to communicate the RPE for each exercise to the client, letting them know how hard this set should feel.
In addition, I would suggest the inclusion of a field where clients record their "Last Set Rate of Perceived Exertion" (LSRPE) This way trainers can get a more granular picture of how and where clients rate of exertion reaches or approaches failure throughout the workout rather than relying on the single exertion rating at the end of the workout.
This could also be tied into automation, automatically generating a tag when clients LSRPE is falling well below the trainer's planned RPE so that more difficult progressions or increased weight could be added to the exercise.
This would create a more fluid channel of communication when dealing with various modalities of strength vs. hypertrophy vs. endurance training. For example if high levels of volume, well short of failure are programmed for a client looking to increase their neuromuscular strength adaptation, the client could feel more assured that they are progressing at just the right pace, even if they're not approaching failure.